Solenoid apparatus

ABSTRACT

An apparatus may include a ferromagnetic housing defining a housing cavity, an electrically-conductive coil disposed in the housing cavity and defining a coil cavity, a ferromagnetic core piece disposed in the coil cavity, a ferromagnetic pole piece comprising a first face in contact with the core piece and a projection extending from a second face of the pole piece opposite the first face, a flexible element defining an opening, where the projection is disposed within the opening and the flexible element is disposed between a portion of the projection and the first face of the pole piece, and a ferromagnetic armature coupled to the flexible element, where the flexible element is disposed between at least a portion of the armature and the first face of the pole piece.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication Ser. No. 62/117,175, filed Feb. 17, 2015 and entitled“Proportional 2-Way Valve”, the contents of which are incorporatedherein by reference for all purposes.

BACKGROUND

Generally, a solenoid converts energy to linear motion. This linearmotion may serve many purposes, including but not limited to operationof a mechanical switch and selective control of one or more fluid paths.Solenoid-based systems exhibit varying degrees of efficiency (force perunit of supplied energy), linearity (i.e., of the efficiency curve),proportionality (i.e., of movement to supplied energy), and hysteresiseffects (which result in different system response depending on whetherthe supplied energy is increasing or decreasing). Depending upon theirintended use, a solenoid and the system in which it is employed aretypically designed to maximize one or more of these characteristics.However, designers face challenges in maximizing one or more of thesecharacteristics while keeping others within desired tolerances.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description is provided to enable any person in the art tomake and use the described embodiments. Various modifications, however,will remain readily apparent to those in the art.

FIG. 1 is a cross-sectional view of an apparatus according to someembodiments.

FIG. 2 is an elevational view of an apparatus according to someembodiments.

FIG. 3 is a bottom-side perspective view of an apparatus according tosome embodiments.

FIG. 4 is an exploded view of an apparatus according to someembodiments.

FIG. 5 is an exploded view of an apparatus according to someembodiments.

FIG. 6 is a bottom-side perspective view of a pole piece according tosome embodiments.

FIG. 7 is a top-side perspective view of a pole piece according to someembodiments.

FIG. 8 is a bottom-side cross-sectional view of a pole piece accordingto some embodiments.

FIG. 9 is a top-side cross-sectional view of a pole piece according tosome embodiments.

FIG. 10 is a cross-sectional view of a pole piece according to someembodiments.

FIG. 11 is a bottom-side perspective view of a pole piece and a movingarmature sub-assembly according to some embodiments.

FIG. 12 is an exploded view of a moving armature sub-assembly accordingto some embodiments.

FIG. 13 is a top-side cross-sectional view of a pole piece and a movingarmature sub-assembly according to some embodiments.

FIG. 14 is a top-side cross-sectional view of a pole piece and a movingarmature sub-assembly according to some embodiments.

FIG. 15 is a top-side perspective view of a moving armature sub-assemblyin a housing according to some embodiments.

FIG. 16 is a bottom-side perspective view of a pole piece in a housingaccording to some embodiments.

FIG. 17 is a top-side cross-sectional view of a pole piece and a movingarmature sub-assembly in a housing according to some embodiments.

FIG. 18 is a cross-sectional view of an apparatus according to someembodiments.

FIGS. 19 through 25 illustrate relationships between coil current andfluid flow for various physical and operational parameters according tosome embodiments.

FIG. 26 is a cross-sectional view of an apparatus according to someembodiments.

FIG. 27 is a cross-sectional view of an apparatus according to someembodiments.

DESCRIPTION

An inventive two-way proportional solenoid apparatus is presentedherein. Some embodiments implement a valve for metering a variety ofworking fluids including gases and liquids. The following description isprovided to enable any person in the art to make and use the describedembodiments. Various modifications, however, will remain readilyapparent to those in the art.

FIGS. 1-5 include cross-sectional, perspective and exploded views of anapparatus according to some embodiments. The depicted apparatus is asolenoid valve, but embodiments are not limited thereto. Embodiments maydiffer from the depicted apparatus in shape, size, components,construction, and/or materials.

The housing (13) is ferromagnetic and is substantially cylindrical inconstruction. The housing (13) contains a coil assembly comprising acoil (18) wound around a bobbin (16). Pins (9) protrude through openingsin the end of the housing (13). Pins (9) are supported by the bobbin(16) and electrically connected to the coil (18). In the illustratedembodiment, an electrical connector (11) plugs onto pins (9) to supplypower to the coil (18) via lead-wires (8). Implementations may utilizeother types of connections to the pins (9) and to the coil (18). Theelectrical connector (11) is retained by a molded plastic cap (22) whichpresses over an end of the housing (13) through which pins (9) protrude.A seal (19) restricts the ingress of moisture into the cap (22). Thelead-wires (8) pass through two holes in the cap (22), which are sealedusing cable seals (10).

A ferromagnetic core piece (12) is disposed within the bobbin (16), andabuts a ferromagnetic pole piece (3). The core piece (12) and the polepiece (3) may comprise different materials (e.g., different grades ofsteel) particularly-suited to their below-described functions. Accordingto some embodiments, the core piece (12) and the pole piece (3) comprisea single integral piece. The ferromagnetic pole piece (3) mates with aportion of a moving armature sub-assembly (5). During operation, and aswill be described below, features of the pole piece (3) facilitate theadvantageous positioning of the moving armature sub-assembly (5) andalso provide improved operational efficiency.

FIGS. 6-9 include various views of the pole piece (3), while FIG. 10provides a more detailed view of its construction. According to someembodiments, a back face of the pole piece (3) (i.e., the face exposedto the core piece (12)) includes a recess filled with a substantiallynon-magnetic material (15). A projection (30) extends from a face of thepole piece (3) opposite the back face.

The recess may be created on the back face prior to machining any of theinternal features of the pole piece (3), and the recess is substantiallyfilled by melting copper therewithin. The material (15) may be selectedfor its structural as well as magnetic characteristics, as it may alsoprovide support to the structure of the pole piece (3). The internalfeatures such as the projection (30) are subsequently created, leaving athin portion of ferromagnetic base material at the base of the recess,as shown in FIG. 10.

According to some embodiments, these features may reduce and/orsubstantially prevent magnetic flux from passing between the outercylindrical surface (17) of the pole piece (3) and the center pole face(23), increasing the amount of magnetic flux contributing to the axialforce experienced by the moving armature sub-assembly (5). Thisphenomenon will be described in more detail below with respect to FIG.18.

Moreover, a sealed chamber (24) is created for a working fluid withoutrequiring additional components and seals. Additionally, since such aworking fluid would not contact the non-magnetic material (15), problemswith fluid compatibility and corrosion may be virtually eliminated.

The aforementioned construction sequence (i.e., create recess, fillrecess with non-magnetic support material, machine internal features)facilitates conforming the internal features of the pole piece (3) totight dimensional tolerances. In this regard, and as mentioned above,certain internal features of the pole piece (3) are used to locate andmate with the moving armature sub-assembly (5).

FIG. 11 is a perspective view of the moving armature sub-assembly (5)coupled to the pole piece (3) according to some embodiments. As shown inthe exploded view of FIG. 12, the moving armature sub-assembly (5)comprises a ferromagnetic armature (6), a guide spring (4), a valvespring (7) and a poppet (2). The poppet (2) further incorporates anelastomeric insert (14) in the center of its exposed face as shown.

The two disk springs (4) and (7) exhibit substantially higher stiffnessin the radial direction than in the axial direction. These propertiesstrongly constrain the armature (6) to move primarily in the axialdirection. According to some embodiments, the guide spring (4) is weldedto the back face of the armature (6), and the valve spring (7) isretained by the poppet (2) which is inserted into the armature (6) andswaged in place.

FIGS. 13 and 14 illustrate the coupling of the pole piece (3) and thearmature sub-assembly (5) according to some embodiments. A portion ofthe projection (30) passes through an opening defined by the guidespring (4), features (31) of the projection (30) contact a centerportion (41) of a first face of the guide spring (4), and an internalcylindrical surface (32) of the pole piece (3) is spaced a smalldistance from a widest outer cylindrical surface (61) of the armature(6). An outer portion of the second face of the guide spring (4) is incontact with the armature (6) at its outer circumference. A face (71) ofthe valve spring (7) abuts a lower rim (33) of the pole piece (3). Theoperational significance of these physical features will be describedbelow.

FIG. 15 illustrates the armature sub-assembly (5) placed within the body(1), and FIG. 16 illustrates the pole piece (3) placed within thehousing (13). As shown in FIGS. 1-3, the body (1) is threaded onto thehousing (13).

As shown in FIGS. 1-4, the body (1) incorporates a tubular orifice (20).The body (1) may be made from a variety of materials including ferrousand non-ferrous metals, plastics and ceramics, depending on therequirements of the application. For malleable materials, one method ofretaining the orifice (20) in the body (1) is to deform the bodymaterial around the circumference of the orifice (20). This both holdsthe orifice (20) in place, and creates a fluid tight seal between thebody (1) and the orifice (20). For plastic and other body materialswhich are not easily deformed, the orifice (20) may be held in place byultrasonic welding, heat staking, adhesive etc.

The external end of the orifice (20) protrudes from the bottom face ofthe body (1) and may be threaded. This may create an industry-standardmounting interface. The interior end of the orifice (20) has a smallopening to limit the maximum flow therethrough. This design allows themaximum flow rating to be changed by using an orifice having adifferently-sized internal opening, and/or by using a differentcombination of springs (7) and (4), which provides a different combinedstiffness in the axial direction.

Each of springs (7) and (4) may exhibit any degree of axial stiffness.In certain implementations, the guide spring (4) is small in diameterand it is therefore difficult for the guide spring (4) to providesignificant stiffness in the axial direction without exceeding thestress limit of its constituent materials. Some embodiments maytherefore utilize a guide spring (4) which is very flexible in the axialdirection, and a valve spring (7) which is much stiffer than the guidespring (4). Embodiments may also or alternatively provide a commonsub-assembly in which the guide spring (4) is attached permanently tothe back of the armature (6), and the valve spring (7) is selected atthe time of assembly, based on the required pressure and flowcharacteristics.

A wave washer (21) positioned between the body (1) and the valve spring(7) is used to press the valve spring (7) into contact with the polepiece (3) and to press the pole piece (3) against an end face of thecenter pole (12). O-Rings (19) seal the interior from the ambientatmosphere.

FIG. 17 is a cross-sectional view showing the body (1), orifice (20),the pole piece (3) and the armature sub-assembly (5), in order to evenmore clearly illustrate construction according to some embodiments. Asillustrated, the elastomeric insert (14) of the poppet (2) closes theinternal opening of the orifice (20), preventing fluid flowtherethrough.

FIG. 18 illustrates operation according to some embodiments. In ade-energized condition (i.e., no electrical current flowing through thecoil (18)), pre-loaded forces in the valve spring (7) push the poppet(2) against the end of the orifice (20) creating a seal. Uponapplication of electrical current, current in the coil (18) generatesmagnetic flux along a path passing through the ferromagnetic housing(13), the pole piece (3), the armature (5) and the core (12), as shown.This magnetic flux traverses the illustrated cylindrical radial air gapbetween the internal cylindrical surface of the pole piece (3) and thecorresponding external surface of the armature (5) and the illustratedconical air gap between the internal surface of the armature (5) and thecenter portion of the pole piece (3).

As a result, the magnetic flux generates a net axial force across theconical air gap as illustrated, attracting the armature (5) towards thepole piece (3), and tending to lift the poppet (2) off the orifice (20).If the magnetic flux, and resulting axial force, is strong enough, thepoppet (3) lifts off the orifice (20) and allows the working fluid toflow in through the center of the orifice (20) and out of the exit portsin the body (1).

The magnetic flux will also create radial forces as it crosses theradial air gap between the internal cylindrical surface of the polepiece (3) and the external cylindrical surface of the armature (5). Theradial forces will substantially cancel each other out if the armature(5) is kept concentric with respect to the pole piece (3) duringoperation. This concentricity is facilitated in some embodiments by theradial stiffness of the disk springs (4) and (7) and the tighttolerances of the internal features of the pole piece (3).

Reducing the amount of magnetic base material by means of a copper (orother non-magnetic material)-filled recess, as illustrated in FIG. 10and FIG. 18, reduces a percentage of the generated of the magnetic fluxwhich passes from the housing (13), through the base of the pole piece(3) and directly into the core (12), without passing through thearmature (5). By reducing this percentage, the amount of axial forceattracting the armature (5) towards the pole piece (3) is increased fora given amount of current applied to the coil (18).

The increased axial force for a given amount of applied current enablesthe use of a stiffer combination of guide spring (4) and valve spring(7). As will be described below with respect to FIG. 21, using a stiffercombination of guide spring (4) and valve spring (7) results in morelinear operation with less hysteresis than a less-stiff combination ofguide spring (4) and valve spring (7). Alternatively, the same guidespring may be used to provide a same linearity and hysteresis asless-efficient designs, but at a lower operating current.

The axial force will increase as the armature (5) gets closer to thepole piece (3). The mating surfaces of both parts are conical in orderto minimize this effect and to therefore increase linearity of arelationship between current and axial force, both during opening (i.e.,lifting the poppet (2) off of the orifice (20)) and closing (i.e.,allowing the poppet (2) to move toward the orifice (20)).

Some embodiments therefore provide a controlled opening between theorifice (20) and the poppet (2), substantially proportional to theelectrical current passing through the coil (18), thus allowing improvedfluid flow control.

FIG. 19 shows relationships between valve fluid flow and coil currentaccording to some embodiments. At low values of coil current, themagnetic force attracting the armature (5) to the pole piece (3) is lessthan the pre-load from the valve spring (7). In this case, the orificeremains closed and only leakage flow passes therethrough. At thedepicted initial current value, the magnetic force is sufficient tobegin to lift the poppet (2) off the orifice (20) and flow starts toincrease. Increasing the coil current above the initial current valueresults in increasing fluid flow up to some maximum value dependent onthe size of the orifice (20).

As shown in FIG. 19, the relationship between fluid flow and coilcurrent is subject to nonlinearities due to inherent nonlinear magneticcharacteristics of the device. This also causes hysteresis, resulting indifferent flow depending on whether the coil current is increasing ordecreasing. By providing more axial force for a given applied currentand maintaining a radial position of the armature as described above,some embodiments exhibit less hysteresis than conventional designs.

The flow characteristics can be selectively modified (e.g., for a givenapplication) by changing the combined stiffness of, and the preloadapplied to, the valve spring (7) and the guide spring (4), and bychanging the orifice opening.

FIGS. 20-22 illustrate effects on the relationship between fluid flowand coil current caused by each of these changes. For example, FIG. 20shows that increasing the preload applied to the valve spring (7)increases the initial current value required for poppet lift-off andreduces the flow output for a given coil current. FIG. 21 shows thatincreasing the combined stiffness of the disk springs (4) and (7) leavesthe initial current value substantially unchanged, while reducing theslope of the current vs. flow characteristic curve. FIG. 22 shows thatincreasing the orifice diameter decreases the initial current valuerequired for poppet lift-off and increases the slope of the current vs.flow characteristic curve.

FIG. 23 also shows changes to the current vs. flow characteristic curvecaused by changing the orifice diameter. However, FIG. 23 assumes thatthe orifice (20) is an outlet and that the incoming fluid arrives at aside port of the housing (1). As shown, increasing the orifice diameterin such a case has an effect which is opposite from the reverse caseillustrated in FIG. 22. That is, increasing the orifice diameterincreases the initial current value required for poppet lift-off anddecreases the flow output for a given coil current.

Preloading the disk springs (4) and (7) will now be discussed in moredetail with respect to FIGS. 24 and 25. In a typical installation, fluidpressure at the inlet to the orifice (20) causes a net force which tendsto lift the poppet (2) off the orifice (20). Thus, as the fluid pressureis increased, the value of current at which the poppet (2) begins tolift off the orifice (20) (i.e., the initial current) decreases. Theamount of force which preloads the valve spring (7) in the oppositeaxial direction on the valve spring (7) may therefore be set such thatthe poppet (2) remains on the orifice (20) at a given maximum ratedpressure.

Referring to FIGS. 26 and 27, the threaded connection between thehousing (13) and the body (1) may be designed to allow some degree ofadjustment. Threading the housing (13) further into the body (1) has theeffect of increasing the preload on the disk springs (4) and (7) andvice versa. The preload may be adjusted in order to achieve a particularinitial opening current for a particular inlet pressure. For example,during assembly, a current slightly above the initial opening current isapplied to the coil (18) and the flow is monitored. The housing is thenthreaded in or out as appropriate to achieve a desired flow for a givencurrent. Using this method, part-to-part variations can be minimized,and devices can be produced with more-consistent initial opening currentor other characteristic(s). According to some embodiments, the interfacebetween the orifice (20) and the body (1) may be threaded in order toadjust the preload by threading the orifice (20) in and out of the body(1).

Although the industry standard may assume that flow will enter throughthe center of the orifice (20), some embodiments may operate with fluidflow in the reverse direction. In this configuration, flow entersthrough the radially offset ports, and exits through the center of theorifice (20). Increasing the fluid pressure in this case causes thecurrent required to lift the poppet (2) to increase.

The velocity of the fluid passing between the orifice (20) and thepoppet (2) causes flow reaction forces which tend to force the poppet(2) towards the orifice (20). Some embodiments minimize these forces bydesigning the poppet (2) to have a much larger diameter than the orifice(20). This larger diameter forces the fluid to flow radially afterexiting the orifice (20) and minimizes the (axial) flow forces.

Embodiments are not limited to the control of fluid flow. The principlesherein may be used to provide a linear motor and/or solenoid usable forany purpose.

Embodiments described herein are solely for the purpose of illustration.Those in the art will recognize other embodiments may be practiced withmodifications and alterations to that described above.

What is claimed is:
 1. An apparatus comprising: a ferromagnetic housingdefining a housing cavity; an electrically-conductive coil disposed inthe housing cavity and defining a coil cavity; a ferromagnetic corepiece disposed in the coil cavity; a ferromagnetic pole piece comprisinga first face in contact with the core piece and a projection extendingfrom a second face of the pole piece opposite the first face; a flexibleelement defining an opening, the flexible element having a first faceand a second face opposite the first face, where the projection isdisposed within the opening and the flexible element is disposed betweena portion of the projection and the first face of the pole piece; aferromagnetic armature coupled to the flexible element, where theflexible element is disposed between at least a portion of the armatureand the first face of the pole piece; the first face of the flexibleelement is in contact with the projection, and the second face of theflexible element is in contact with the armature; and a portion of thesecond face of the flexible element which is in contact with thearmature moves axially during axial movement of the armature, and aportion of the first face of the flexible element which is in contactwith the projection is substantially stationary during axial movement ofthe armature.
 2. An apparatus according to claim 1, wherein the portionof the second face of the flexible element which is in contact with thearmature is an outer portion of the flexible element and the portion ofthe first face of the flexible element which is in contact with theprojection an inner portion of the flexible element.
 3. An apparatusaccording to claim 1, wherein the portion of the projection comprises asubstantially conical surface.
 4. An apparatus according to claim 3,wherein a surface of the armature facing the substantially conicalsurface is substantially conical.
 5. An apparatus according to claim 1,wherein the pole piece comprises an internal surface defining a polepiece cavity, and wherein the flexible element and a portion of thearmature are disposed within the pole piece cavity.
 6. An apparatusaccording to claim 5, further comprising; a second flexible elementcoupled to the armature and to the pole piece, wherein the portion ofthe projection and at least the portion of the armature are disposedbetween the flexible element and the second flexible element.
 7. Anapparatus according to claim 6, wherein the flexible element and thesecond flexible element are substantially circular and exhibit higherradial stiffness than axial stiffness.
 8. An apparatus according toclaim 7, wherein the portion of the projection comprises a substantiallyconical surface, and wherein a surface of the armature facing thesubstantially conical surface is substantially conical.
 9. An apparatusaccording to claim 1, wherein the flexible element is a disk spring andexhibits higher radial stiffness than axial stiffness.
 10. An apparatusaccording to claim 1, wherein the core piece is composed of a firstmaterial and the pole piece is composed of a second material differentfrom the first material.
 11. An apparatus comprising: a ferromagnetichousing defining a housing cavity; an electrically-conductive coildisposed in the housing cavity and defining a coil cavity; aferromagnetic core piece disposed in the coil cavity; a ferromagneticpole piece comprising a first face and an internal surface defining apole piece cavity, the first face comprising a first ferromagneticportion in contact with the core piece and a recess comprisingsubstantially non-magnetic material; a ferromagnetic armature, where aportion of the armature is disposed within the pole piece cavity; aflexible element coupled to the ferromagnetic armature, the flexibleelement having a first face and a second face opposite the flexibleelement first face, where the flexible element is disposed between theportion of the armature and the first face of the pole piece; the secondface of the flexible element in contact with the armature; and a portionof the second face of the flexible element which is in contact with thearmature moves axial during axial movement of the armature.
 12. Anapparatus according to claim 11, wherein a thickness of ferromagneticmaterial defining a lower portion of the recess is less than thethickness of the first ferromagnetic portion in contact with the corepiece.
 13. An apparatus according to claim 11, further comprising: aprojection extending from a second face of the pole piece opposite thefirst face; wherein the flexible element defines an opening, and whereinthe projection is disposed within the opening and the flexible elementis disposed between a portion of the projection and the first face ofthe pole piece.
 14. An apparatus according to claim 13, the first faceof the flexible element is in contact with the projection.
 15. Anapparatus according to claim 13, wherein the portion of the projectioncomprises a substantially conical surface.
 16. An apparatus according toclaim 15, wherein a surface of the armature facing the substantiallyconical surface is substantially conical.
 17. An apparatus according toclaim 13, further comprising; a second flexible element coupled to thearmature and to the pole piece, wherein the portion of the projectionand at least the portion of the armature are disposed between theflexible element and the second flexible element.
 18. An apparatusaccording to claim 11, wherein the core piece is composed of a firstmaterial and the pole piece is composed of a second material differentfrom the first material.